FRANKLIN, Tenn. (AP) — A Franklin man's backyard became one of 11 Tennessee sites added to the National Register of Historic Places this week after archaeological digs there turned up one of the two oldest human settlements ever documented in the state.

Excavations last fall of Paul Litchy's backyard, also known as the Coats-Hines site, found the remains of bones and artifacts that prove humans were there before 12,000 B.C, near the end of the last ice age.

While the bones and artifacts are important, the Coats-Hines site is nationally significant because it is a rare instance in which archaeologists can show ancient people interacting with animals, state prehistoric archaeologist Aaron Deter-Wolf told The Tennessean (http://bit.ly/qQrDFh).

"That's really the meat of archaeology," Deter-Wolf said. "It's the association of the items and not just the items themselves."

Archaeologists believe there was a pond in Litchy's backyard where animals, including mastodons, were killed by hunters.

The oldest human settlement in Tennessee is known as the Johnson Site, along the Cumberland River east of Nashville.

The first excavations began at Coats-Hines 1977, and a dig in 1994 revealed the only known example in the southeastern U.S. of mastodon remains directly associated with human-made stone tools in an undisturbed context, Deter-Wolf said.

Last fall, archaeologists and students from Middle Tennessee State University turned up human artifacts, pollen samples and more than 1,500 animal bones that can be traced to a variety of species. And archaeologists from the Center for the Study of the First Americans at Texas A&M are now planning excavations at the site.

"Coats-Hines is extremely important to our understanding of both Tennessee and the Nashville area's ancient past," Deter-Wolf said. It "has the potential to provide important new information on initial human migration into North America, the tools these earliest Americans used, the food they ate and how they adapted to the changing environment at the end of the last ice age."

Litchy, a part-time civil and environmental engineering instructor at Vanderbilt University, didn't know about the land's historic significance when he bought the property in 1998. Today, he's low-key about the artifacts, some of which are less than 1/8th of an inch in size.

"They show me a little piece of something or other and I think, 'So what?' " Litchy said, laughing. "I tell them, 'When you guys are excited, tell me so I can be excited with you.' "